The electrochemistry of DPPH in three-phase electrode systems for ion transfer and ion association studies

The three-phase electrochemistry of 2,2-diphenyl-1-picrylhydrazyl (DPPH) has been studied by attaching a droplet of nitrobenzene (NB) containing DPPH to a graphite electrode in an aqueous electrolyte solution. Since DPPH can be reduced to DPPH− and oxidized to DPPH+, the accompanying ion transfer to NB and ion pair formation in NB are accessible. The anion transfer from water to nitrobenzene is accompanied by the formation of ion pairs [DPPH+An−] with nitrate, hexafluorophosphate, perchlorate and trichloroacetate. The ion pair formation of DPPH− with tetrabutylammonium cations is very weak. When the DPPH is dissolved in molten paraffin together with the salt tetrabutylammonium tetrafluoroborate (TBATFB), and composite electrodes are produced by mixing the paraffin with graphite powder, DPPH exhibits a typically surface electrochemical response providing a rather stable system DPPH/DPPH−.